Hitherto, as the method for transferring a toner image formed on an organic photoreceptor onto a recording material to form a final image, a method has been known by which the toner image formed on the organic photoreceptor, herein after occasionally referred to photoreceptor, is directly transferred on to the recording material. On the other hand, an image forming method employing an intermediated transferring member has been known. According to such the method, a transferring step is further inserted in the process for transferring the toner image from the organic photoreceptor to the recording material. Namely, the toner image is primarily transferred from the organic photoreceptor onto the intermediate transferring member and then the primarily transferred toner image on the intermediate transferring member is secondarily transferred to the recording material to obtain the final image. Of these, the intermediate transfer system is frequently applied for piling transfer of toner images each having different color in a full color image forming apparatus by which a colored original image is separated and reproduced by subtractive color system employing black, cyan, magenta and yellow toners.
However, problems relating to the intermediate transferring member have been occurred in the foregoing intermediate transfer system. One of these is that carrier particles adhered to the photoreceptor is pushed into the photoreceptor by the pressure by the intermediate member and causes a crater-like damage having swollen on both sides on the surface of the photoreceptor. The crater-like damage causes damage on cleaning blade. As a result of that, the cleaning of the toner is made insufficient and slipping of the toner through the cleaning blade and line-shaped image defects are occurred. Such the phenomena further cause partially lowering of the sensitivity and the transfer ability of the toner so that a image defects such as partially lacking of character image so called as interior lacking are occurred and sharpness of the image tends to be degraded.
Besides, technique for lowering the surface energy of the intermediate transferring member by supplying a solid lubricant to improve the secondary transfer of the toner from the intermediate transferring member to the image recording material is disclosed in, for example, Japanese Patent Publication Open to Public Inspection (JP-A) Nos. 6-337598, 6-332324 and 7-271142. However, such the lowering of the surface energy of the intermediate transferring member is insufficient for improving the total transferring ability of the image forming system having two-step transfer process employing the intermediate transferring member since such the lowering of the surface energy of the intermediated transferring member causes decreasing of the transfer ratio of the from the photoreceptor to the intermediate transferring member. It is found that further improvement is required for forming copy images under a high temperature and high humidity condition or for a prolonged period.
Namely, it has been found as to the system employing the intermediate transferring member that it is necessary to totally improve both of the primary and secondary transfer by improvement of the surface property of both of the organic photoreceptor and the intermediate transferring member.